I have a Runtime 100.4 .NET application that needs to use an offline geoprocessing service, via a Local Server installation calling a GPK geoprocessing package.

I've successfully started the local server, started and displayed a map service (from an MPK package and from an MPKX package), and even started a geoprocessing service from a GPKX package. However, I need to start a service that's in a GPK package (to execute a tool that's in Desktop but not Pro). When I point the app to that one, it fails with the error below.